1. Field of the Invention
Apparatuses consistent with the present invention relate to an optical disc reproducing apparatus, and more particularly, to an optical disc reproducing apparatus supporting various Run Length Limited (RLL) codes such as RLL(2,1), RLL(1,7) and RLL(1,10), wherein the optical disc reproducing apparatus compensates for minute asymmetrical features of a partial response (PR) (abcde) channel, and a PR signal and supports an accurate detection of data, a jitter measurement and a signal synchronization, and a 16 level 5-tap Viterbi decoder.
2. Description of Related Art
With the multimedia era beginning, needs for storing and transmitting a large quantity of digital data have been increased. Accordingly, an optical disc such as a digital video disc (DVD) has been boomingly studied in the art these days. The current DVD market is steadily growing, being divided into a computer industry that desires to adopt a DVD read only memory (DVD-ROM) and a home appliance industry that intends to promote a DVD-video. Additionally, the DVD extends an applicable sphere accordingly, as a DVD-recordable (DVD-R), a DVD-rewritable (DVD-RW) and a DVD-random access memory (DVD-RAM) appear on the market.
Such kinds of conventional optical discs may be often confronted with problems as follows. When data stored in the optical disc are reproduced, analog radio frequency (RF) signals under reproduction may frequently exhibit an asymmetric waveform. Furthermore, this asymmetric phenomenon may give rise to other unfavorable phenomena such as a jitter, a non-linear bit offset, a direct current (DC) offset, and an inter-symbol interference (ISI) between symbols of reproduced data. Such phenomena often make it difficult to execute a detection and a correction of frequency errors and phase errors, thus causing the distortion of reproduced signals. A related art optical disc reproducing apparatus has typically used a digital sum value (DSV) algorithm to correct such asymmetric errors.
However, the related art DSV algorithm does not always execute an exact correction of the asymmetric errors under various code environments such as RLL(1,10) and RLL(2,10). For example, the related art DSV algorithm may often fail to exactly detect asymmetric errors in the case of 4T sampling signals reproduced in the variable frequency oscillator (VFO) sector of the optical disc.
Furthermore, the related art optical disc reproducing apparatus does not support an integrated solution for both RLL(1,10) and RLL(2,10) codes. Therefore, two separate and independent code detectors, namely, adding an RLL(1,10) detector to an existing RLL(2,10) detector, are used to support the integrated solution. This configuration of the detectors may, however, be inefficient in circuit area use and power consumption.
Also, according to the related art optical disc reproducing apparatus, as a signal of a high frequency is amplified, a signal interference phenomenon occurs. Accordingly, the signal may not be identified. Also, accurately measuring a signal quality and estimating a frequency may not be easily executed.
Also, according to the related art optical disc reproducing apparatus, when a feature of the signal is deteriorated, accurate signal models of both an equalizer and a Viterbi decoder may not be set up. Accordingly, a signal detecting operation may not be accurately executed.
Also, according to the related art optical disc reproducing apparatus, a related art DSV algorithm does not detect and compensate a minute DC offset information in a record reproducing channel. Accordingly, frequency and phase errors may not be detected and compensated. Also, a phase locked loop (PPL) operation may be unstably executed.
Also, according to the related art optical disc reproducing apparatus, when the feature of the signal is deteriorated, a frequency estimating operation may not be executed.
Also, according to the related art optical disc reproducing apparatus, the related art optical disc reproducing apparatus may not correspond to various kinds of signal patterns in a high-speed Viterbi detector.